Copyright Statement

Abstract

Tetraploid Pacific oysters (Crassostrea gigas) are commonly used within aquaculture to generate predominantly
sterile triploids for commercial use. Unlike triploids, tetraploids are fertile and can be spawned with each other to
maintain a commercial breeding population. The impacts this hatchery perpetuation has on the genetic diversity
of the tetraploid population and subsequent commercial triploid product are currently unknown. This study determines
the diversity (number of alleles and heterozygosity), pedigree assignment and effective population size
over two generations of tetraploid production. A significant drop in diversity was observed over two successive
generations of tetraploid oysters spawned in 2008 and in 2011, likely due to different numbers of broodstock
used. Similar to diploids, pedigree assignment in tetraploids showed unequal parental contributions and an effective
population size smaller than the census population, thus the potential for inbreeding to occur in the future
is high.